3D TV systems that are on the market today are typically stereo-based: one image is presented to the left eye and another to the right eye. There are several ways to achieve this effect. For instance, polarizing filters can be used on every second row of the TV together with polarized glasses. Another way is to quickly alternate the left and the right image on the screen and have the user wear shutter glasses that are synchronized with the screen. Digital cinemas today often use a polarization filter in front of the projector. The filter can change direction every 120th of a second or more, which allows time multiplexing to work together with relatively inexpensive polarized glasses.
However, consumers do not like to wear glasses, and this may be the reason why 3D TV is now seen as a failure within the TV industry. Therefore new TV screens that do not require glasses are emerging.
Glasses free 3D display can be achieved by using a lenticular array in front of the screen. This makes it possible to make some pixels visible only from certain angles. In the simplest form, a lenticular display can be created to have every second column of pixels visible only by the left eye and the remaining columns only visible by the right eye. However, this requires the viewer to be positioned in a very tightly defined sweet spot in front of the display.
Another solution is to use steerable displays that rely on eye-tracking. By finding the position of each eye of the viewer, the display can control the lenticular array so that it is always sending the left image to the left eye and the right image to the right eye. If this is combined with rendering the content from the correct position the effect could be very convincing in theory.
A disadvantage with both of these types of two-view screens is that they can only be used by one viewer at a time, since there are only one sweet spot.
One way to get around the single viewer problem is to use a multi-view display. This is a display that is capable of sending out several different views in different view angles. For example, multi-view displays marketed by Dimenco are capable of sending out a viewer cone of 27 different views. This means that the viewer can move his/her head a bit within the viewer cone and does not need sit exactly in a sweet spot. However, there need to be several views between the eyes of the viewer otherwise both eyes will sometimes see the same view and there will be no 3D experience. Hence, the viewer cannot move the head very far from the sweet spot and outside of the viewer cone.
A further multi-view display solution is to use a very large viewer cone presenting different views at different view angles. One example is the Holografika display Holovizio 80WLT, which has about 85 different views spread over 180 degrees.
Whereas the Holografika display solves many of the drawbacks of other cone-based multi-view displays, it suffers from two major problems: content creation and storytelling/bad seating.
For content creation the problem is that in order to get really good data to feed to the system, you ultimately want to have one camera for every view that the multi-view display can display. An example of this is shown in FIG. 1. Herein, a camera rig 40 with 90 cameras 41 is used to capture the scene 9 and thereby produce 90 different images that can be sent out by a multi-view display at different view angles.
For instance, the left eye of a first viewer 5, see FIG. 2, will see the video captured from camera #44, the right eye will see camera #45, and a second viewer 6 will look at the video captured from cameras #20 and #21. Such a camera rig 40 comes with a number of drawbacks. Firstly, it is huge, which makes it hard to transport and to operate in confined spaces or in environments such as in a thick jungle. Secondly, all those cameras 41 makes the camera rig 40 expensive. Thirdly, the cameras 41 have to be calibrated relative to each other. For instance, the cameras 41 may be supposed to all be pointed at a point in space, but flexibilities in the camera rig 40 may cause them to deviate slightly from this. Even small such errors must be compensated for in software, and the bigger the camera rig 40 is, the harder it is to make it stable.
A related problem of using a camera rig 40 with many cameras 41 is that more raw data is needed than if simple 2D video were used. Compression can help a bit since many of the views are similar. However, with the compression techniques available today, the number of bits to provide an extra view does not go to zero with increasing number of views, instead bit rate increases linearly with the number of views.
The second problem has to do with storytelling. Assume you have a movie that wants to convey to you the feeling that you are asked to join the U.S. army. Uncle Sam is pointing directly at you, and saying “I want YOU for the U.S. army!”. This is simple to film using a regular 2D camera: you just let the actor look straight into the camera, and perhaps point at it, when saying the phrase. The effect will be that anyone watching the 2D video will feel that Uncle Sam is looking straight at them, irrespectively of where they are in the room when watching. With a camera rig such as the one shown in FIG. 1 it is less straight-forward. Which camera 41 should the actor be pointing at? If he points at the middle camera, only the viewer sitting right in front of the multi-view display screen 2 (first viewer 5 in FIG. 2) will feel as if Uncle Sam is pointing and looking at him/her. Meanwhile, the second viewer 6, who is sitting off-center, will feel like Uncle Sam is pointing at someone else, i.e. at the first viewer 5, and will not feel exposed. This is because the second viewer 6 sees the output of one of the left cameras but the actor 9 is pointing towards the middle camera, see FIG. 1.
In summary, the more views used, the higher fidelity the end result will be, becoming a true holographic experience in the limit. However, as more views are added, more cameras 41 are needed for the camera rig 40, making it more complicated and expensive. In addition, more data needs to be stored and transmitted. Perhaps worst of all, an increased number of views does not solve the storytelling problem, namely that the viewers 5, 6 get different experiences depending on where they sit in front of the multi-view display 2.
Hence, there is room for the improvement within the field of multi-view displays.